It's not bacteria or algea, I'm used to the rusty color from that, but my sponge turned the color of the word red in my first post, and it will not rinse out at all.
The only meds I have are MelaFix and PrimaFix (and some ICH meds which I haven't used since I put this sponge in).
Other stuff that I put in my tank is some aquarium salt, FloraPride (with water changes), StressCoat and StressZyme (irregularly or when using tap water)
I was just about to say that I haven't been using anything new, but I do remember adding Amquel with Buffers(ph
) when I moved my tank down. I've use Amquel PLUS before and never had anything like this. I don't really think the Amquel is the culprit, but other than changing to sand, that's the only thing I've done different in my tank